Behavior of seismic base isolated high-rise buildings under the effect of different earthquakes

Earthquakes induce significant stresses and deformations in the structural systems of multi-story and especially high-rise buildings, posing substantial threats to both structural safety and occupant comfort. Seismic base isolation is an effective engineering solution developed to mitigate these effects by damping the seismic energy efficiently, thereby enabling structures to respond more safely during seismic events. In this study, nonlinear time history analyses were conducted to compare the seismic behavior of multi-story and high-rise reinforced concrete structures with rigid supports and seismic base isolation systems. Ground motion acceleration records were utilized in these time history analyses for the 1999 Kocaeli-Gölcük, 2023 Kahramanmaraş-Pazarcık, and 1977 Kastamonu earthquakes that occurred previously. For these analyses, the structures were designed as 6, 12, and 24-story buildings. In this context, the effects of different numbers of stories, different earthquakes, and seismic base isolation on the seismic behavior of the structure were investigated. In the analyses, single-curvature friction pendulum-type isolators were taken into account as isolators, and the loads on the isolators were defined in accordance with the regulation. The base shear forces, top of buildings' peak displacements, structural periods, mass participation ratios, absolute displacements, relative displacements, and story accelerations occurring in the structure were examined by obtaining the results of structural analyses. As a result of the analysis, it was seen that the base isolation system significantly reduced the displacements, accelerations, peak displacements, structure frequency and base shear forces and better protected the structure from seismic effects. In high-rise buildings, isolators have been shown to effectively reduce seismic effects on lower floors, while their effects on upper floors remain limited. In contrast, rigid-supported structures are more exposed to seismic effects and have a higher risk of damage. As a result of the study, it was observed that the base isolation system effectively controls the displacement amplitudes at the top of the structure, story accelerations, and base shear forces, providing a more balanced and safe performance.